1. Field of the Invention
The present invention relates to a light radiation device which radiates light onto a radiation object site for performing tests or the like on the appearance, damage or the like of a product, a light source device, and a light connection mechanism or the like which is suitably used for the connection thereof.
2. Description of the Related Art
Conventionally, as disclosed in Japanese Unexamined Patent Publication No. 5-248820 (1993), a system is known in which a light beam is guided from a light source device such as a halogen lamp to a light radiation device via an optical fiber bundle made of a plurality of bundled optical fibers, and the light beam is radiated from this light radiation device to illuminate a piece of work. According to such a system, owing to the intervention of optical fibers, the light radiation device will have an improved degree of freedom in placement, compactification, and others irrespective of the size and shape of the light source device.
Further, in these kinds of light radiation devices, as disclosed for example in the aforementioned publication, a system is known in which light emission ends of optical fibers are held to surround a ring-shaped fiber holding member, and a light beam is directly radiated from the light emission end of each optical fiber onto a piece of work placed at the center under the fiber holding member so as to illuminate the piece of work from the surroundings. Also, since a light beam that escapes to the outside is generated at each light emission end in the above-described construction in which the light from the light emission end is directly radiated onto the piece of work, a system has been developed in which a ring lens having a ring-like shape is placed under the light emission end and the light beam is refracted by this ring lens so as to prevent the light beam from escaping, thereby making improvements in the light condensing efficiency, as disclosed in Japanese Unexamined Patent Publication No. 5-199442 (1993).
On the other hand, regarding the light source device, since the halogen lamp is hardly sufficient in terms of light intensity stability, lifetime, quick responsiveness and the like in view of the efficiency and precision in these types of product tests, a light source device using an LED has been developed as a new light source device that can make improvements on these points. Specifically, there is Japanese Unexamined Patent Publication No. 2000-21206 previously proposed by the applicant of this application. This is a light source device in which numerous LEDs are disposed on a substrate; one end of an optical fiber is bonded to the front surface of each of these numerous LEDs; and the other ends of the optical fibers are bundled and drawn out to the outside of the device body so that the light beams from the LED can be taken out via these optical fibers.
Meanwhile, in recent years, there is an increasing demand that requires precision testing by conducting bright illumination on an extremely small site such as a semiconductor chip or a soldering part of the semiconductor chip onto a printed substrate, as a piece of work to be tested. For this reason, there is a demand for condensing the light beams in a greater degree so as to radiate brighter light beams onto the radiation object site more efficiently.
However, in view of these aspects, these types of light radiation devices as taught in the prior art are insufficient in terms of light condensing area, light condensing efficiency and others. For example, in the light radiation device disclosed in Japanese Unexamined Patent Publication No. 5-199442 (1993), although the light beams can certainly be prevented from escaping to the outside by the ring lens, the circumferential components of the light beams emitted from the fiber are not refracted at all and hence are not condensed though the radial (relative to the ring lens) components of the light beams are refracted and hence are condensed, thereby providing insufficient light condensation onto a minute area. Furthermore, in the light source device disclosed in Japanese Unexamined Patent Publication No. 2000-21206, there is a limitation in introducing the light emitted from an LED efficiently into optical fibers. In addition, if the light intensity of the light source device is unreasonably raised in order to cover the above-described drawbacks, the problem of heat generation will disadvantageously increase.
Thus, a principal desired object of the present invention is to provide an illumination system of this kind for tests and others which has, on the light radiation device side, a structure that can outstandingly improve the light condensing degree and the light condensing efficiency as compared with the prior art and, on the light source device side, a structure such that the light from an LED can be introduced extremely efficiently into optical fibers and the light can be made into light suitable for illumination, whereby the current demands of tests on a piece of work can be fully satisfied in view of the light condensing area and the light condensing efficiency while making the best of the characteristics of the system in which the light radiation device and the light source device are separated with an intervention of the optical fibers.
Thus, the light radiation device according to the present invention is a light radiation device for radiating onto a radiation object site a light beam introduced via an optical fiber bundle made of a plurality of optical fibers, the light radiation device having a box that houses a fiber holding section for holding a light emission end of each of the optical fibers in a discretely disposed state and a lens holding section for holding a lens one by one proximate to or close to the light emission end of each of the optical fibers.
According to such a device, one lens is mounted onto each optical fiber in a one-to-one correspondence, so that the light condensing area can be easily made smaller. Further, since the lens can be easily disposed proximate to or close to the light emission end of the optical fiber, the light emitted from the optical fibers can be refracted without leakage, and can be radiated onto the radiation object site at an extremely high efficiency. As a result of this, one can reasonably meet the demand that requires precision testing on an extremely small site such as a semiconductor chip or a soldering part of the semiconductor chip onto a printed substrate.
Here, it is sufficient that the lenses are functionally separated one by one in respective correspondence with the optical fibers, so that the lenses need not necessarily be physically separated one by one. For example, it suffices if convex lenses are connected to each other at the peripheries thereof with the use of a thin plate or the like, thereby forming a physical integration of a plurality of convex lenses.
As a suitable embodiment for condensing the light with a fewer number of components, it is preferable that an axial line of the optical fiber at the light emission end coincides with an optical axis of the corresponding lens, and the axial line and the optical axis of the lens are directed to the radiation object site.
On the other hand, in order to make a contribution to the degree of freedom in production or the like, it is also preferable that an axial line of the optical fiber at the light emission end is shifted from an optical axis of the corresponding lens, and the optical axis of the light beam emitted from the light emission end is deflected by the lens to be directed to the radiation object site.
In order to perform condensation of light more suitably and to carry out an adjustment of focal distance more easily in accordance with the distance from the light source device to the radiation object site and the size of the radiation object site, it is preferable that the light radiation device is constructed in such a manner that the light beams each emitted from each light emission end via the lens are collimated into parallel light beams that are generally parallel to each other, wherein a single second lens is provided to be positioned between the lens and the radiation object site so that a radiation light beam emitted from each of the lenses is refracted by the second lens to be condensed to the radiation object site. This is because, with such a device, the focal distance can be freely changed simply by exchanging the second lens with another. This second lens may be, for example, a convex lens or a Fresnel lens.
A specific embodiment preferable for illumination used for tests or the like is, for example, a light radiation device in which the box has an observation hole for observing the radiation object site, and a plurality of the fiber holding sections are provided either intermittently or at equal spacing along a circumferential direction of the opening periphery to function as fiber holding holes for inserting and holding the optical fibers.
Further, a specific embodiment of the lens holding section is, for example, a lens holding hole provided in correspondence with the fiber insertion hole for housing and holding the lens. The lens suitably held by such a lens holding hole is, for example, a so-called ball lens having a spherical shape.
In order to achieve simplification or the like of the assembling work, it is desirable that the fiber holding hole penetrates through a cylindrical member having the same cross-sectional shape as the lens holding hole and that the cylindrical member is fitted into an anti-radiation-site side of the lens holding hole having the lens inserted therein. Here, though the cylindrical member is preferably a circular cylinder in view of production, the cylindrical member may else have another shape such as a triangular prism or a quadrangular prism as long as it has the same cross-sectional shape. Here, if a fiber holding hole is formed along the central axis of the cylindrical member, the optical axis of the lens can be made to coincide with the axial line of the optical fiber as described above. In contrast, if a fiber holding hole is disposed at a site shifted from the central axis, the optical axis of the lens will be shifted from the axial line of the optical fiber, so that the optical axis of the radiation light can be deflected via the lens in a direction different from the direction of light emission from the optical fiber. In other words, even if the axial line of the optical fiber at the light emission end is not set to be directed towards the radiation object site, the optical axis of the radiation light can be directed towards the radiation object site.
Thus, the above-described light radiation device produces effects such as an outstanding improvement in the light condensation degree as compared with the prior art. Further, a light source device that makes the above-described effects more conspicuous by making a pair with this light radiation device and can supply light efficiently and reasonably to the light radiation device is, for example, a light source device for supplying a light beam via a light guiding member such as an optical fiber bundle made of a plurality of bundled optical fibers or a glass rod, the light source device having a common casing that houses a first light source lens for collimating radiation light beams emitted from a single or a plurality of LED(s) into generally parallel light beams and a second light source lens for condensing the light beams from the first light source lens to introduce the condensed light beams to a light introduction end of the light guiding member.
According to such a device, the light that could not be collected into the light introduction end as in the prior art can be condensed and collected, so that the light from the LED can be supplied to the optical fiber bundle and hence to the light radiation device with an extremely high efficiency. Further, since the position of mounting the LED or the like is not restricted, adjacent LEDs can be placed in a dense state when the LEDs are disposed in a large number, whereby the quantity of light can be increased for that amount, and a light source device that can emit a stronger light beam can be constructed without unreasonableness. Further, the device can be easily formed as a small (handy-type) device being convenient for carriage, so that not only an improvement in the handling property such as transfer of the light radiation device can be achieved but also a light source device having a size that meets the needs can be produced at a low cost, thereby providing advantages both in terms of use and in terms of costs. Moreover, in the case where long optical fiber bundles (light guides) are drawn about for radiation of light to a piece of work, it can advantageously prevent damages such as breakage of the optical fiber bundle, thereby providing an advantage in durability.
Also, another embodiment that can produce similar functions and effects maybe, for example, a light source device for supplying a light beam via a light guiding member such as an optical fiber bundle made of a plurality of bundled optical fibers or a glass rod, wherein a substrate is provided with a single or a plurality of LED(s), a first light source lens for collimating radiation light beams each emitted from each of the LED into generally parallel light beams is respectively disposed on a radiation surface side of each of the LED, a second light source lens for condensing the generally parallel light beams from the first light source lens to introduce the condensed light beams to a light introduction end of the light guiding member is disposed forward of each of the first lenses, and light emission ends of the optical fibers equal in number to the LED are bundled to form an assembling section.
In order to improve the efficiency of collecting the light emitted from the LED as much as possible and to make the light condensing area, which is an area of the eventually condensed light that has passed the light radiation device, as small as possible, it is preferable that the LED is single in number (only one LED is provided), that the first light source lens is made of a light condensing member being transparent and having an approximately conical shape with a larger diameter at the light emission end, and that a recess for allowing the radiation section of the LED to enter is formed at the light emission end of the first light source lens.
The light radiation device and the light source device described above can be connected to each other with an optical fiber bundle; however, in some cases, depending on the object of use, a light radiation unit in which these light radiation device and light source device are integrally formed as a unit by using a common box may be preferable in view of usability.
Now, in the case where such a light radiation device and a light source device are connected with an optical fiber bundle, when light is introduced into the optical fiber bundle from the light source device, the intensity of light introduced into each optical fiber, for example, may be different from one another, or if a multi-color LED is used, the color of light introduced into each fiber may be different from one another. This may cause occurrence of intensity unevenness or color unevenness of light eventually emitted from the light radiation device. In order to prevent this in advance, it is preferable that the light introduced into each optical fiber is uniform. In order to achieve this, there may be a construction having a light connection mechanism that connects the optical fiber bundle on the light source device side to the optical fiber bundle on the light radiation device side so as to mix the light in this light connection mechanism. A specific embodiment thereof may be a light connection mechanism provided with a light passageway having a circular cross-section for passing a light beam and a reflection/refraction section disposed on an outer perimetric surface of the light passageway for reflecting or refracting the light beams inward, wherein end surfaces of the light passageway are disposed respectively close to an end surface of an optical fiber bundle on a light source device side and an end surface of an optical fiber bundle on a light radiation device side with coincident axial centers, and a diameter of the light passageway is set to be generally equal to a diameter of each of the optical fiber bundles.
Now, regarding such a light source device, various other ones can be considered. In particular, by allowing a light source device to include a cooler, one can lower the temperature of the LED thereby promoting the stabilization of light quantity, the increase in the lifetime, and others to a greater extent. Embodiments of such a light source device will be given below.
Namely, one can consider, for example, a light source device in which numerous light emitting bodies are densely spread over a substrate; a first light source lens for collimating radiation light beams each radiated from each of the light emitting bodies into generally parallel light beams is disposed on the radiation surface side of the light emitting body; a second light source lens for condensing the generally parallel light beams from the first light source lens and introducing the condensed light beams to the light introduction end of a light guiding member is disposed forward of the first light source lens; and the light source device is further provided with a cooler for cooling the back surface of the substrate.
According to such a device, by providing a construction in which the radiation light beams each radiated from each light emitting body are converted into generally parallel light beams by the first light source lens and the converted generally parallel light beams are condensed by the second light source lens as described above, the light that could not be collected into the light introduction end as in the prior art can be condensed and collected as well. Further, since the positions of mounting the light emitting bodies and the like are not restricted as in the prior art, adjacent light emitting bodies can be disposed in a dense state. Further, by cooling with the cooler the back surface having a larger area where no light emitting bodies are mounted among the front and back surfaces of the substrate, the decrease in the light intensity caused by a temperature rise of the light emitting bodies can be restrained with good efficiency, and moreover, occurrence of troubles such as deformation of lenses or substrate can be prevented.
If the light emitting bodies are made of light emitting diodes and resistances connected to the light emitting diodes are disposed on the outer peripheries of the substrate, the heat generated from the resistances can be made hardly transferable to the light emitting diodes by using the outer peripheries of the substrate where no light emitting diodes are present and disposing the resistances at these places.
If the first light source lens is constructed with an array of lenses each disposed in correspondence with each of the light emitting bodies, the radiation light from each light emitting body can be converted into generally parallel light with certainty.
If a Fresnel lens is used as the second light source lens, the lens can be made smaller and lighter as compared with a general convex lens, and in addition, since the Fresnel lens can be easily processed, it can be easily made into a quadrangle or subjected to a drilling treatment. Moreover, since it is a thin lens, the Fresnel lens can be placed closer to the light emitting body side, thereby enhancing the efficiency in collecting the light into the light introduction end of the light guiding member.
If the cooler is constructed with a Peltier element disposed on the back surface side of the substrate, a heat dissipation fin disposed on the side of the Peltier element opposite to the substrate side, and a heat dissipation fan for supplying a cooling air towards the heat dissipation fin, one can allow the heat generated in the Peltier element to be dissipated thereby cooling the substrate with good efficiency. By using the Peltier element, the light emitting diodes can be cooled with certainty even if the density of mounting the light emitting diodes is increased or even if a large electric current flows to increase the amount of heat generation by increase in the number of light emitting diodes. This realizes increase in the lifetime of light emitting diodes, and the like.
If the light source device is provided with a temperature sensor for sensing the temperature of the substrate and is provided with temperature controller for controlling the electric current supplied to the Peltier element for letting the sensed temperature from the temperature sensor be a set temperature so as to maintain a constant temperature, an improvement in white balance can be realized, for example, in the case where white light is emitted with the use of light emitting diodes of three primary colors. Here, among the light emitting diodes of three primary colors, the blue light emitting diode gives a higher brightness according as the temperature rises, while the red light emitting diode and the green light emitting diode give a lower brightness according as the temperature rises, thereby lowering (deteriorating) the white balance.
If the light emitting diodes are made of chip-type light emitting diodes and a reflector is disposed on the radiation surface side of the chip-type light emitting diodes, the light that cannot be collected can be collected by the reflector while being able to increase the mounting density as compared with the light emitting diodes of bullet type (also referred to as a discrete type). The chip-type light emitting diodes are meant to include, for example, those of surface mount device type having a pair of electrodes (cathode and anode) provided on the front and back of a base via a through-hole (which may be absent), and else, those having bare chips of light emitting diodes directly mounted on a substrate.
If the light emitting diodes are controlled to be energized with the use of a pulse control signal, the durability of the light emitting diodes can be improved as compared with continuous driving.
If a camera is provided for capturing an image of reflected light reflected by radiation of light from the light emitting diodes onto a test object or transmitted light transmitted through the test object, and the light emitting diodes are controlled to be energized for energizing the light emitting diodes at the time or before the shutter of the camera is opened and for de-energizing the light emitting diodes when a predetermined period of time passes after closing the shutter, then the brightness while the light emitting diodes are energized can be raised by allowing a large electric current to pass while the shutter is open. In addition, since the light emitting diodes are not energized when the shutter is closed, the generation of heat can be restrained to the minimum.
If light emitting diodes of three primary colors, i.e. red light emitting diodes, green light emitting diodes and blue light emitting diodes, are arranged in a predetermined order on the substrate, the light beams obtained by condensation of light beams radiated from these light emitting diodes and radiated through a light guiding member can be made into (uniform) white light having a good balance.
The light source device may be provided with a casing that houses a substrate on which a single or a plurality light emitting body (bodies) are densely spread, a first light source lens for collimating the radiation light beams radiated from the light emitting bodies into generally parallel light beams, and a second light source lens for condensing the generally parallel light beams from the first light source lens to introduce the condensed light beams to a light introduction end of a light guiding member; and the light source device may be provided with a power source cord for supplying electric power to the light emitting bodies; and the light source device may be provided with a cooler for cooling the back surface of the substrate, thereby constructing a small (handy-type) light radiation device being convenient for carriage.
According to such a device, by providing a construction in which the radiation light beams radiated from light emitting bodies are converted into generally parallel light beams by the first light source lens and the converted generally parallel light beams are condensed by the second light source lens, the light that could not be collected into the light introduction end as in the prior art can be condensed and collected as well. Further, since the positions of mounting the light emitting bodies and the like are not restricted as in the prior art, adjacent light emitting bodies can be disposed in a dense state if the light emitting bodies are to be disposed in a large number. Further, by cooling with a cooler the back surface having a larger area where no light emitting bodies are mounted among the front and back surfaces of the substrate, the decrease in the light intensity caused by a temperature rise of the light emitting bodies can be restrained with good efficiency, and moreover, occurrence of troubles such as deformation of lenses or substrate can be prevented. Further, by providing a small (handy-type) device being convenient for carriage, not only an improvement in the handling property such as transfer of the light radiation device can be achieved but also a light radiation device having a size that meets the needs can be produced at a low cost.
If the light emission end of the casing is allowed to include a tubular holding section for inserting and holding the light guiding member so that the optical fiber bundle set to have a dimension having approximately the same tip end as the tip end of the holding section may be inserted into and held by the holding section, then optical fibers which are expensive can be used at a low cost, and an improvement in the handling property can be achieved as compared with long ones.
If the cooler is constructed with a heat dissipation fin formed on a part of or on the whole of the casing so as to discharge the heat of the substrate to outside of the casing, the number of components can be reduced as compared with the case of fabricating and assembling the casing and the heat dissipation fin separately.
If the device is constructed in such a manner that the light emitting body is single in number, that the first light source lens is made of a light condensing member being transparent and having an approximately conical (almost like a trumpet) shape with a larger diameter at the light emission end, and that a recess for allowing the radiation section of the light emitting body to enter is formed at the light introduction end of the first light source lens, then the light beams that could not be collected by an ordinary lens among the light beams emitted from the radiation section of the light emitting body can be reflected at the light reflection layer provided on the outer perimeter of the light condensing member to increase the quantity of light entering the second light source lens.
If the device is constructed in such a manner that numerous light emitting bodies having a substrate are provided, that a first light source lens for collimating the radiation light beams each radiated from each of the light emitting bodies into generally parallel light beams is disposed respectively on the radiation surface side of each of the light emitting bodies, that a second light source lens for condensing the light beams from the first light source lens to introduce the condensed light beams to the light introduction end of a light guiding member made of a single or a plurality of bundle(s) is disposed forward of each of the first light source lens, that an assembling section is constructed by bundling the light emission ends of the light guiding members equal in number to the light emitting bodies, and that a cooler is provided for cooling the back surface of the substrate, then by providing a construction such that the radiation light beams radiated from the light emitting bodies are converted into generally parallel light beams with the first light source lens so as to condense the converted light beams with the second light source lens, the light beams that could not be collected into the light introduction end as in the prior art can be condensed and collected as well. Further, the light beams from the light emitting bodies can be introduced with good efficiency and with certainty to the light introduction end of the light guiding member such as a single (one) optical fiber or an optical fiber bundle made of a plurality of bundled optical fibers having a smaller diameter than the single one. By using the optical fiber bundle, the flexibility can be enhanced, and the light beams can be radiated more uniformly onto the radiation section to which the light beams are to be radiated, as compared with the case where the light guiding member is constructed with a single optical fiber. Further, by cooling with the cooler the back surface having a larger area where no light emitting bodies are mounted among the front and back surfaces of the substrate, the decrease in the light intensity caused by a temperature rise of the light emitting bodies can be restrained with good efficiency, and moreover, the lifetime of the light emitting bodies can be increased and occurrence of troubles such as deformation of lenses or substrate can be prevented.
Furthermore, if the light introduction end of a second light guiding member for guiding the light from the assembling section to an arbitrary position is disposed at the light emission end of the assembling section, then the light can be radiated to a desired radiation position simply by moving the light emission end of the second light guiding member. Here, it is preferable to construct the second light guiding member with a flexible material such as an optical fiber. In addition to an embodiment in which two lenses, namely the first light source lens and the second light source lens, are provided, there may be an embodiment in which a single lens is used which is an integration of these two lenses.
On the other hand, if for example a piece of work that is not always at a constant position is to be radiated such as pieces of work that are disposed without precisely being positioned on a conveying device and successively conveyed, then a function of the ability to move the light radiation device frequently in accordance with the position of each piece of work is demanded on the light radiation device. Further, optical fibers are also naturally entrained and moved by frequent movement of the light radiation device. Because the optical fibers have flexibility, the flexibility of optical fibers was thought to meet such usage as this movement to a full extent in the prior art.
However, in actuality, optical fibers are bulky and heavy as compared with electric wires or the like, and particularly if long (for example, two to three meters or more) optical fibers are used, a larger driving mechanism may be needed in order to move the light radiation device while drawing the optical fibers around, or the movement or position control of the light radiation device may become difficult. Further, since optical fibers are inferior in flexibility as compared with electric wires and are broken in a comparatively short time by being frequently bent or moved, problems may be raised on the reliability, lifetime or the like of the device. In contrast, if an LED attracting people""s attention in recent years as a substitute for a halogen lamp are used as a light source and numerous LEDs are directly mounted on a light radiation device without the use of optical fibers, a problem may be raised such as difficulty in scale reduction of the light radiation device or condensation of light. For example, in the case where an extremely small member such as a component mounted on a printed substrate is to be radiated, if the minimum light condensation diameter is large such as in a light radiation device on which the LED are directly mounted, useless sites may be radiated as well thereby failing to provide an efficient illumination.
Then, in order to completely abandon the idea that the light radiation device should be moved by using the flexibility or free extendibility of optical fibers as in the prior art and to solve the above-mentioned inconveniences at a stroke without deteriorating the advantages regarding the less heaviness or compactness that the LED light source device has, an illuminating testing system is preferable, which includes a light radiation device having an emission outlet of light to be radiated onto a radiation object site and being supported on a movable supporter that can be moved, an LED light source device that receives electric power for light emission via an electric cable from a power source disposed separately from the movable supporter and is mounted on the movable supporter, and one or a plurality of flexible optical fiber(s) that introduce the light from the LED light source device via outside to the emission outlet of the head.
According to such a device, since weight reduction and compactification of the LED light source device can be easily achieved, one can make driving of the movable supporter and hence the light radiation device little affected though the LED light source device is mounted on the movable supporter.
Further, if the light radiation device is fixed onto and supported by the movable supporter so as not to change the relative positional relationship between the LED light source device and the light radiation device, the load on the optical fibers can be reduced, and the influence on the reliability, lifetime or the like can be avoided. Of course, the light source device may be constructed to move slightly or move slowly relative to the movable supporter as long as no problems are raised on the reliability, lifetime or the like of the optical fibers.
Further, since the light radiation device is connected to an optical fiber and is separated from the LED light source device, a super scale reduction of the light radiation device can be achieved and light beams can be condensed onto a small area. Also, since the light source and the radiation object site or the image capturing device for capturing an image of this radiation object site can be spaced apart to some extent, the heat generated by the light source can be prevented from giving adverse effects on the radiation object site or the image capturing device.
On the other hand, to the LED light source device, electric power may be supplied from a battery being present in the device or accompanying the device, or alternatively, electric power may be supplied to the LED light source device via an electric cable from a power source provided separately from the movable supporter. According to the former construction, a cableless device can be achieved. According to the latter construction, though an electric cable is needed, the movable supporter and the light radiation device can be driven with an extremely small load as compared with the load of entraining and moving the optical fibers as in the prior art as well as with a high reliability, since electric cables are far more superior to optical fibers in terms of flexibility, durability, costs and others. Still alternatively, one can consider a construction in which electric power is supplied from the image capturing device.
Further, by disposing the light source device near to the radiation outlet, the optical fibers can be made short (for example, 1 m or less) and less heavy. If the device is constructed as such, the light radiation device can be driven without unreasonableness even if the light radiation device is movably supported by the movable supporter. In this case, the light radiation device is preferably constructed to move slightly or move slowly relative to the movable supporter as long as no problems are raised on the reliability, lifetime or the like of the optical fibers.
In order to improve the light condensation property, a device having a lens mounted on the tip end of the optical fiber on the light radiation device side is preferable.
A preferable embodiment of the electric cable may be a robot cable.